1. Field of the Invention
The present invention relates to novel polyorganosiloxanes containing, per molecule, at least one siloxyl unit substituted with at least one group having one or more sterically hindered piperidinyl functional groups, devoid of toxicity upon contact with the skin.
The present invention also relates to an improved cosmetic composition comprising the polyorganosiloxanes according to the invention and the use of these compositions for the treatment of keratin materials, in particular the skin and the hair.
2. Description of Related Art
Numerous cosmetic compositions comprise polyorganosiloxanes (“silicones”). Polyorganosiloxanes may be used to provide a conditioning effect on the hair or the skin. Polyorganosiloxanes may also be used for sensory effects, termed cosmetic effects, during their application to the skin, the hair or the lips.
Accordingly, it has been proposed to use, in cosmetic compositions, polyorganosiloxanes of numerous different chemical structures, which may optionally contain different functional groups.
Linear polydimethylorganosiloxanes (PDMS) may be used as sensory agents on the skin, as protecting agents which act as a barrier against water, as defoaming agents, as agents for removing creamy whiteness from cosmetic compositions appearing during a first rubbing on the skin or the hair “desoapers”, as conditioners and as emollients.
Cosmetic compositions comprising aminated polyorganosiloxanes have also been described, often in combination with benefits in terms of coloration. The presence of aminated groups improves the affinity of polyorganosiloxane for the hair and provides good conditioning of the hair, for compositions intended to be rinsed off or not to be rinsed off.
For example, the documents U.S. Pat. No. 6,605,577 (Chemsil Silicones Inc.), U.S. Pat. No. 6,642,194 (Chemsil Silicones Inc.), WO 03/088939 (The Procter & Gamble Company), WO 03/066007 (Dow Corning), describe cosmetic compositions comprising a polyorganosiloxane bearing specific functional groups.
In the entire description, the expression “keratin materials” will be understood to mean the materials to be cosmetically or dermatologically treated, chosen from the skin, the scalp, the hair, the eyelashes, the eyebrows, the nails and the mucous membranes.
In the entire description, the expression “leave-in” cosmetic or dermatological product will be understood to mean any product whose application to the keratin materials to be treated is not followed by rinsing with water.
In the entire description, “rinse-off” cosmetic or dermatological product will be understood to mean any product whose application to the keratin materials to be treated is followed by rinsing with water.
Numerous compositions for washing keratin materials have been described in the prior art. Accordingly, patent application FR-A-2 848 829 describes detergent compositions essentially intended for washing the hair, which exhibit improved cosmetic properties, in particular in terms of disentanglement, smoothing, suppleness, malleability and softness of the hair. These compositions comprise at least one amphoteric surfactant alkylamphohydroxyalkyl sulfonate, and at least one silicone chosen from nonorganomodified silicones having a viscosity ranging from 500 mm2/s to 1 000 000 mm2/s and organomodified silicones.
Patent application CA-1 201 952 describes surfactant compositions intended for the formulation of cosmetic compositions, in particular shampoos, whose foaming power is improved. These compositions comprise:                from 3.75 to 15% by weight of an anionic surfactant such as a lauryl ether sulfate,        from 1 to 4.20% by weight of an amphoteric surfactant such as an alkyl amidobetaine,        from 0.7 to 3% by weight of a nonionic surfactant such as a polyoxyethylenated sorbitan, and        from 0.1 to 4% by weight of a “soap” chosen from fatty acids, alkyl isethionates, alkyl taurides and alkyl sarcosides.        
Patent application US 2004/0197287 describes antidandruff shampoos whose detergent and antidandruff properties have been improved. These compositions comprise:                from 5 to 50% by weight of a detergent surfactant,        from 0.1 to 4% by weight of an antidandruff agent,        from 0.1 to 50% by weight of a fatty acid ester, and        polyoxyethylenated sorbitan, and        at least 20% by weight of water.        
Patent application WO 97/33561 describes cleansing compositions for the hair and the skin, which exhibit a low degree of eye irritation. These compositions comprise:                from 5 to 20% by weight of a mixture of surfactants including a nonionic surfactant, an amphoteric surfactant and an anionic surfactant, and        from 0.01 to 3% by weight of a humectant agent, such as in particular a cationic polyol.        
Finally, patent application FR-A-2 886 145 describes compositions for washing keratin materials, in particular the hair, comprising, in a cosmetically acceptable aqueous medium, at least one anionic, nonionic or amphoteric detergent surfactant, at least one cationic polymer and at least one aminated silicone comprising an amine functional group carried by a sterically hindered group. These compositions make it possible to improve the properties of visual and tactile smoothness of the hair, while having good washing and foaming power.
It is known in the prior art that certain components of cosmetic or healthcare products, such as chemical preservatives, perfumes, colorings, chemical sunscreens, ethanol and the like, can cause problems of skin irritation and/or intolerance, or even problems of contact allergy. Sensitive or reactive skins are skins which easily react to allergens or irritants following skin permeability disorders linked to impairment of the barrier function of the stratum corneum and a disequilibrium in the production of epidermal cytokines. Modification of skin permeability gives rise to the appearance of subjective and objective signs.
The appearance of the objective signs is particularly observed during the use of common cosmetic or healthcare products. They are defined by sensations of itching, tightness, prickling, heat, stinging and burning. The objective signs are revealed in an irregular manner by xerosis, by seborrhoeic dermatitis, by telangiectasia, by scales, by a blotch, by vesicles or by an edema.
According to specialists, the subjective and objective signs may appear for a short period immediately after the application of the cosmetic product, or may appear transiently, or alternatively may last longer, for the whole day or intermittently during the day. Accordingly, these signs may be discrete or severe and may require medical advice.
Accordingly, the compositions described in the prior art may exhibit certain inadequacies. In particular, the highest performing shampoos can cause prickling in the eye when the dilute product runs into the ocular sphere, which occurs frequently in children. Moreover, a good number of these shampoos may cause in people with sensitive skin reactions of discomfort, such as blotches, itching or prickling. That may be the case for certain amino silicones comprising an amine functional group carried by a sterically hindered group and described for example in patent application FR-A-2 886 145. These amino silicones, more commonly called “silicones HALS”, may exhibit problems of skin sensitization and are classified as sensitizers “R43”. Now, cosmetic raw materials exhibiting a skin sensitization character are restricted to very limited usage depending on the countries (see for example for Europe: European Cosmetics Directive No. 76/768/EEC).
For example, in Europe, according to the criteria of Annex VI of the Directive 67/548/EEC in its 28th adaptation to technical progress (2001/59/EC), a chemical substance or preparation is classified as a skin sensitizer “R43” when it can cause sensitization upon contact with the skin. The sensitization upon contact with the skin must have been observed in a significant number of people or via an appropriate test on animals.
Several test methods thus exist using guinea pigs: the Magnusson & Kligman or Buehler tests. Recently, the “Local Lymph Node Assay” (LLNA) test was validated and adopted by the scientific community and presented in the form of the OECD Guideline 429 or of the method described in annex V of the directive 67/548/EEC in its 29th adaptation to technical progress (2005/73/EC). This test is performed on mice and is based on the induction of the proliferation of lymphocytes in the ganglions subjacent to the site of application of the substance. The results determine whether the raw material tested should be classified as sensitizer R43.